The DoD Other Transaction Guide effectively says that regardless of the acquisition pathway, program offices must follow the applicable DoDI for that acquisition pathway when buying via OTs. DoD interim policy was issued for DoD software acquistion on Jan 3rd of this year; review this policy to find the acquisition pathway for software.

https://www.acq.osd.mil/ae/assets/docs/USA002825-19%20Signed%20Memo%20(Software).pdf

DoDI 5000.80, Operation of the MTA, is the instruction for MTA, and it can be accessed in the following link.

https://www.esd.whs.mil/Portals/54/Documents/DD/issuances/dodi/500080p.PDF?ver=2019-12-30-095246-043

DoD OT Guide:  The determination of whether OTs are subject to DoD Instruction (DoDI) 5000.02 depends upon the acquisition pathway selected by the program office. OTs are neither inherently subject to, nor exempt from DoDI 5000.02. Instead, the selection of the award instrument should be considered a separate, but complementary decision. Therefore, any program executed under the DoDI 5000.02 pathway is subject to DoDI 5000.02 policy once this pathway is selected, regardless of whether an OT or traditional contract is used. Similarly, any program executed under the Middle Tier of Acquisition (MTA) pathway, in accordance with Section 804 of the National Defense Authorization Act for Fiscal Year 2016, is subject to MTA policy.